1. Field of the Invention
This invention is related in general to the field of applying fluid samples to analysis strips. In particular, this invention relates to an automatic pipetting apparatus for applying multiple fluid samples to a microporous support medium such as a cellulose acetate or agarose strip which may be used in the field of zone electrophoresis and with other separation techniques including the field of thin layer chromatography. Zone electrophoresis is the science of moving charged particles in an electric field through a solid or semi-solid medium. The technique is most commonly used in medical research and medical laboratories for analyzing various blood proteins.
2. Description of the Prior Art
In the electrophoresis technique, a blood or other fluid sample is applied to a support medium which is then subjected to an electric field so as to separate the components of the sample. The support media used in the electrophoresis process includes cellulose acetate, agar, agarose and acrylamide gels. In laboratory work it is desirable that a plurality of samples be applied to the support medium such that each of the samples may be subjected to the electric field at the same time.
The samples may be applied to the support medium one at a time in serial fashion with a hand pipetter, but the hand pipetter must be rinsed with a cleansing agent and blotted before a new sample is aspirated and then applied to the strip.
Applicators have been designed to apply fluid samples simultaneously or in "parallel" to the strips. Such applicators are described at page 61 of the General Products Catalog for 1984-1985 of Helena Laboratories with offices in Beaumont, Texas. Such applicators may apply eight, twelve or more samples to a microporous support medium and have the advantage of making the electrophoresis technique easier and more reproducible.
The applicators known prior to this invention however have been essentially non-automatic applicators and required cleaning of the applicator tips after each application to the support medium.
Automatic dispensing systems are known in the prior art. For example, a system sold under the trademark "Well Washers" of BioTech Instruments, Inc. of Burlington, Vermont provides an alignment mechanism by which a row of eight or twelve barrels may be positioned above one of a plurality of rows of washing vials or wells. Automation in the system provides selection of dispensing fill volumes, soaking times and number of wash cycles.
None of the prior art however has provided an apparatus for automatically filling a plurality of pipetters from a respective plurality of fluid chambers and then precisely applying such fluid samples from each pipette to a support medium. Another disadvantage of the prior art systems is that there has been no means for automatically washing and cleaning the barrels during each cycle time so as to prevent contamination of each of the barrels during application of a new plurality of fluid samples to a new support medium.
Another disadvantage of the prior art is that there has been no means for precisely automatically applying a very small amount--of the order of one micro liter of sample liquid--to a support medium.
Another disadvantage of the prior art is that there has been no means for precisely automatically diluting a very small amount--of the order of one micro liter--of sample fluid with a diluting liquid, and precisely applying a very small amount of the diluted sample to a support medium.